1. Field of the Invention
This invention relates to a connector for a coaxial cable and more particularly to the connector suitable for a small diameter coaxial cable.
2. Description of the Related Art
FIGS. 1 and 2 are cross-sectional views illustrating examples of the conventional connectors for a coaxial cable. The connectors of this type have two control and outer contacts as typified by, for example, an SMA (Sub-Miniature type A) connector as shown in FIG. 1. This connector comprises a center conductor 27 to be connected to a center wire 20 of a coaxial cable 21, a socket surrounding the center conductor 27 to hold it along with an inner insulator 25, and a outer conductor 26 for terminating the socket and a shielding wire 23, which is the outer conductor, extending from an outer cover 22 in conjunction with a nut 24.
The outer conductor 26 and nut 24 of the coaxial connector, the socket part being an insulator, and the outer conductor 27, are manufactured by machining process.
In contrast to the above-described coaxial connector, there are coaxial connectors composed of parts produced by pressing instead of machining process in order to reduce the cost of the parts. Such coaxial connectors are disclosed in Japanese Patent Application Laid-Open No. Hei 1-140572. As illustrated in FIG. 2, the coaxial connector comprises a center conductor 29 serving as an inner conductor which is produced by punching by press, a metal cylinder 32, which is produced by press-molding and which serves as a part of an outer conductor, an plastic insulator 33 surrounding the conductor 29, molded from plastic resins, an inside resin part 30 composed of molding resins for fixedly holding a shielding wire, and a shrinkable tube for covering the shielding wire.
Since this coaxial connector can be automatically assembled from parts produced at low cost by pressing or by molding resins, the coaxial connector can be produced at a low price.
The former coaxial connector has the drawback that the most parts are manufactured by machining, as de scribed above, and hence, a large amount of manpower is required, resulting in high cost. On the other hand, although the latter coaxial connector can be produced by automated machines, it has the drawback that it still requires many number of parts and its cost may not be as low as expected. In addition, the center conductor of the center conductor is not symmetrical in shape with respect to the axis of the coaxial cable. The complicated shape of the inner conductor results in difficulty in matching impedance and a reduction in transmission characteristics. Further, although the advantage of a coaxial cable is the concentric arrangement of the center conductor and outer conductor, this advantage is eliminated by the unsymmetrical shape and the characteristic impedance of the coaxial cable cannot be ensured, leading to the occurrence of distortion in the transmission waveform.